Furry Crocodile - Dog. Furry crocodiles fall in to three main & distinct categories:
They do exactly what they say on the tin... sort of. Most of the time they spend sleeping - not unlike their handlers (in civilian employment most certainly). The military guard dog is a different boiling vessel-full of poissons entirely, and is generally a highly-trained beast. Its senses are honed to a fine edge through regular bouts of bestial masturbation and tins of Winalot. They are intensely loyal to their handlers.
Do not stroke, and do not show your MOD90 to it on the gate.
Be afraid... be very afraid. If one of these four-legged torpedoes locks on to your ARRSE, it's generally assumed that you're fucked. Unless, that is, you've had sneaky-beaky specialist training from THEM.
Specialist anti-dog measures include staying out of their line-of-sight (i.e. above it), staying upwind (or is it downwind?) of the search line, or simply by slotting it with your Rambo knife - or a pointy stick. Do not attempt to masturbate - either the dog or yourself (though by this point, I can't see the harm in cracking one off for ol' time's sake).
Sometimes Retrievers, sometimes Labradors, often Spaniels. Occasionally a bizarre mixture of all three. I like Spaniels - indeed I now have one myself; but the joy of being bounced upon and licked by these lovable hounds evaporates immediately when your bergen is ripped off your back by the Singaporean Police and the Arrivals Lounge is filled with your stinking underwear and jazz mags. Spaniels like stinking underwear apparently. Something I wish I'd (and no doubt my now ex-girlfriend had) known in the first place.
More a sub-category of the above, they are apparently trained to seek out the most easily embarrassed person in a Departure Lounge and bury their nose into that person's crotch while everyone laughs. For added effect they may hump your leg. Originally this was for the amusement of the dog handler. However in these days of high security air travel, this is now used as light relief for stressed travellers.
Note: For those of you who believe in reincarnation, the crotch hound may have been a Royal Marine in a previous life.